A conventional blower-vacuum apparatus is disclosed in U.S. Pat. No. 4,870,714. According to the disclosed apparatus, an air suction port and an air discharge port are formed in a main body, so that the air suction port is in confrontation with a fan disposed in the main body and the air discharge port is positioned perpendicularly with respect to an axis of the fan. In a vacuum mode, the air suction port is connected to a suction tube (vacuum nozzle) and the air discharge port is connected to a dust bag. By rotation of the fan, air and dust is introduced into the suction tube and directed into the dust bag through the main body. In the blower mode, the suction tube is detached from the air suction port, and a filter is attached to an open end of the air suction port for preventing dust from being introduced into the main body. Further, the dust bag is detached from the air discharge port, and an air blower tube (blower nozzle) having a tapered shape in which a diameter is gradually reduced toward its tip is connected to the air discharge port. Accordingly, air passing through the filter and introduced into the main body is blown outside through the air blower tube.
However, each time the blower-vacuum apparatus disclosed in the U.S. Pat. No. 4,870,714 is switched between the vacuum mode and the blower mode, the suction tube and the filter must be exchanged and the dust bag and the air blower tube must be exchanged, which is troublesome.
Japanese Utility Model Application laid open publication No. Hei 4-80454 discloses a dust collecting apparatus in which a suction tube (vacuum nozzle) extending in a axial direction of a fan is connected to a main body, and an outlet tube extending in a direction perpendicular to the axis of the fan is connected to a dust bag through a joint. The joint is provided with a branch pipe to which a blower tube (blower nozzle) is connected through a rubber tube. A blower opening of the blower tube is positioned close to a suction opening of the suction tube. Air and dust introduced into the suction tube is directed into the dust bag through the main body, the outlet tube, and the joint. A part of the suction air is also directed to the blower tube through the branch pipe, so that the air is blown to a position close to the opening of the suction tube. Because of this air, rubbish and dust accumulated in indentations on the ground is blown out of the indentations to facilitate suction of the flying rubbish and dust into the suction tube.
However, the dust collecting apparatus disclosed in the laid open Utility Model Application publication No. Hei 4-80454 blows air during suction cleaning work so that a part of the suction air sucked through the suction tube is utilized for air blowing. Accordingly, the blowing air may contain dust, thereby lowering the dust-collecting efficiency of the device. Further, the device is not designed to operate in a blower mode only.
Japanese Utility Model laid open application publication No. Hei 3-92454 discloses a dust collecting apparatus in which one end of an air feed tube is connected to a blower and another end of the air feed tube is connected to a confluence tube which is connected to a dust bag. The confluence tube includes an air feed passage, a dust suction passage and a branch passage. Further, a pivotable change-over valve is provided in the confluence tube. The air feed passage approximately linearly connects the air feed tube and the dust bag. The dust suction passage branches off the air feed passage and has one end connected to a cleaning tube. The branch passage connects the air feed passage to the dust suction passage. In a vacuum mode, the change-over valve is pivotally moved to a position for closing an opening of the branch passage, so that the air from the blower is directed to the dust bag by way of the air feed tube, and the air feed passage. Because of this air flow, air in the dust suction passage is subjected to sucking, and therefore, the dust is sucked through the top end of the cleaning tube and is collected in the dust bag. In a blower mode, the change-over valve is pivotally moved to a position for closing an opening of the air feed passage, so that the air from the blower is directed to the cleaning tube by way of the air feed tube and the branch passage.
However, because the dust collection apparatus disclosed in the Japanese Utility Model Application publication No. Hei 3-92454 is designed to suck ambient air by flowing air, in comparison with the blower vacuum apparatus disclosed in U.S. Pat. No. 4,870,714, in which suction can be exclusively performed, suction power will be inferior assuming that the dust collection apparatuses have power sources with identical output. Further, since the pivotable change-over valve is directly exposed in the passage, dust and rubbish may become entangled in the valve and render the change-over valve inoperable.
Another conventional blower vacuum apparatus is shown in FIGS. 15 and 16. The apparatus includes a main body 310, a blower nozzle 330, and a vacuum nozzle 340. The main body 310 includes a fan case 313 accommodating a fan 319, a motor case 314 accommodating a motor 320, and a dust case 315 positioned below the motor case 314. A handle 312 is provided above the fan case 313. The fan case 313 has an upper wall in confrontation with the fan 319, and the upper wall is formed with grid like air inlet ports 313a. The dust case 315 is connected to a dust bag 350. The motor 320 has an output shaft 321 whose one end is connected to the fan 319. Another end of the output shaft 321 is connected to a cutter blade 318 positioned within the dust case 315.
The blower nozzle 330 extends in a direction perpendicular to the rotation axis of the fan 319, and has one end attached to the main body 310 and another end formed with an air blowing port 330a. The vacuum nozzle 340 extends in parallel with and integrally with the blower nozzle 330 and has one end attached to the main body 310 and another end formed with a suction port 340a. A change-over valve 373 is rotatably supported within the blower port 330a of the blower nozzle 330. The change-over valve 373 can be changed over between a vacuum mode position in which the valve shuts off the blower port 330a as shown in FIG. 15 and a blower mode position in which the valve opens the blower port 330a as shown in FIG. 16.
In the blower mode, if the change-over valve 373 is rotated to its blower mode position and the fan 319 is rotated, air is introduced into the fan case 313 through the grid like air inlet ports 313a formed at the upper wall of the fan case 313. The introduced air passes through the blower nozzle 330 and is blown outside out of the air blowing port 330a. In the vacuum mode, the change-over valve 373 is changed over to the vacuum mode position. However, similar to the blower mode, the rotation of the fan 319 introduces air into the fan case 313 through the air inlet ports 313a, and the introduced air passes through the blower nozzle 330 and is directed toward the air blowing port 330a. The air impinges on the change-over valve 373 and is turned reversely as indicated by an arrow A in FIG. 15. Thus, the air is fed into the vacuum nozzle 340. Because of the air stream, ambient air around the suction port 340a of the vacuum nozzle 340 is sucked because of the creation of negative pressure into the vacuum nozzle 340 as indicated by arrows B. Accordingly, dust can be sucked from the suction port 330a and the sucked dust is directed toward the cutter blade 318 as indicated by arrows C and is pulverized thereat, and is then collected in the dust collection bag 350.
However, in the conventional blower-vacuum apparatus shown in FIG. 15, powerful suction force cannot be provided, because suction of ambient air is achieved by the air stream similar to the dust collection apparatus described in the Japanese laid open Utility Model application publication No. Hei 3-92454. Further, dust may become entangled with the change-over valve rotatably supported at the air blowing port 330a so that change in operation mode may become difficult or impossible to perform.
It is therefore, an object of the present invention to provide a blower-vacuum apparatus capable of providing a strong suction force with a direct suction of air from a vacuum nozzle by rotation of a fan without utilization of suction of ambient air around the air stream, and capable of performing a smooth mode changing operation without adhesion or entanglement of dust in a change-over mechanism.